The present invention relates to increasing the reliability of storage media. In particular, the present invention relates to methods and apparatus for reducing particulate contamination in removable storage media.
Particulate contamination has been discovered as a significant cause of failures of removable storage media, such as removable disk cartridges. Examples of such contaminants include dust, hair, organic compounds, food crumbs, smoke particles, and the like. These particles often cling to the surface of disks within disk cartridges and adhere to the surface, even when the disks are spinning around at the operating speed, for example 5000 rpm to 7500 rpm.
Conventional storage habits contribute to particulate contamination. Removable disk cartridges are designed to be repeated inserted and removed from disk drives. When not in use, these disk cartridges are often stored on dusty shelves, in lint filled pockets, in piles next to computers, and the like. Seldom are disk cartridges returned to the relatively "clean" disk cartridge holders. This typical user behavior often causes a great number of particulate contaminants to adhere to the outside casing of these disk cartridges. When these disk cartridges are inserted into a disk drive, the particles are then introduced into the interior of the disk drive, and thus onto the disk itself.
Particulate contamination can cause defects on the disk and cause irreversible disk drive hardware damage. As is known, conventional read/write heads that transfer data from disks are often very delicate and "fly" over the surface of the disk at a very low height. Contaminants on the surface of a disk that strike the read/write heads at the operating rpm are often sufficient to knock the read write heads out of alignment. As can be expected, the size of the contaminants that can cause such damage decreases as the physical size of the read/write head decreases and the data density of the disk cartridges increase.
One previous method to reduce the number of particulate contaminants on a disk is found on conventional 3.5" floppy disks. This solution has been to provide a particulate trapping material (filter material) on at least one inner surface of a floppy disk. The filter material is typically in the same size and shape as the disk media. Because the disk media is flexible and undulates while being operated, the disk media often bends sufficiently to touch the filter material. The portion of the disk that touches the filter material thus has reduced particulate contamination. A further enhancement has been to force at least a portion of the filter material towards the disk so as to cause the filter material to touch the disk at particular locations.
One drawback to these solution is that excessive amounts of filter material must be used. The filter material must be formed in substantially the same size and shape as the disk media because the locations where the disk media will bend and touch the filter material are unpredictable. The filter material is thus typically placed at all possible places the disk may bend and touch the filter material.
Other drawbacks to these solutions include that having a filter material in constant contact with the disk causes increased abrasion of the disk and increased torque required for the disk drive motor. As is expected, having the filter material in constant contact with the disk also causes a physical drag on the rotation of the disk. To compensate for the increased drag, the torque provided by the drive motor of the disk drive must be increased, otherwise the disk drive motor may burn out prematurely. The increased torque requirement translates to a higher cost for the drive motor.
Other drawbacks to these solutions include the increased abrasion and heating to the disk and subsequent effects on long term storage characteristics of the disk, and the like.
What is thus required are improved methods and apparatus for reducing particulate contamination in removable disk cartridges without significant effects on drive performance.